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  • Syntactic sugar in PHP with static functions

    - by Anna
    The dilemma I'm facing is: should I use static classes for the components of an application just to get nicer looking API? Example - the "normal" way: // example component class Cache{ abstract function get($k); abstract function set($k, $v); } class APCCache extends Cache{ ... } class application{ function __construct() $this->cache = new APCCache(); } function whatever(){ $this->cache->add('blabla'); print $this->cache->get('blablabla'); } } Notice how ugly is this->cache->.... But it gets waay uglier when you try to make the application extensible trough plugins, because then you have to pass the application instance to its plugins, and you get $this->application->cache->... With static functions: interface CacheAdapter{ abstract function get($k); abstract function set($k, $v); } class Cache{ public static $ad; public function setAdapter(CacheAdapter $a){ static::$ad = $ad; } public static function get($k){ return static::$ad->get($k); } ... } class APCCache implements CacheAdapter{ ... } class application{ function __construct(){ cache::setAdapter(new APCCache); } function whatever() cache::add('blabla', 5); print cache::get('blabla'); } } Here it looks nicer because you just call cache::get() everywhere. The disadvantage is that I loose the possibility to extend this class easily. But I've added a setAdapter method to make the class extensible to some point. I'm relying on the fact that I won't need to rewrite to replace the cache wrapper, ever, and that I won't need to run multiple application instances simultaneously (it's basically a site - and nobody works with two sites at the same time) So, am doing it wrong?

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  • Interview Questions in OOP

    - by Fero
    Hi all, I faced the below interview questions in OOP under PHP language. Kindly clear my clarifications regarding this. I am very confused. As i am a beginner to OOP i got too confused. Could anyone clarify these things clearly? Difference between Abstract class and interface. Interviewer : Let us consider abstract class contains three abstract methods such as a,b,c and interface contains three methods a,b,c. In this case these do the same functionality. Then why are going for abstract and why are we going for interface. Me : ? static keyword. Interviewer: We call static method without creating object by using scope resolution operator in PHP. As well as we can able to call concrete methods also. Then what is need of static keyword there? Me : .... final keyword. Interviewer: Give me any scenario of using final keyword. Me : For db connection related method Interviewer: Other than that? Me: ... Constructor. Interviewer: What is the use of constructor? Me : There is no need for object to access this. It will call automatically when the class calls. Interviewer: Other than that? Me : .... Thanks in advance...

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  • Dependency Inversion Principle

    - by Chris Paine
    I have been studying also S.O.L.I.D. and watched this video: https://www.youtube.com/watch?v=huEEkx5P5Hs 01:45:30 into the video he talks about the Dependency Inversion Principle and I am scratching my head??? I had to simplify it(if possible) to get it through this thick scull of mine and here is what I came up with. Code on the marked My_modified_code my version, code marked Original DIP video version. Can I accomplish the same with the latter code? Thanks in advance. Original: namespace simple.main { class main { static void Main() { FirstClass FirstClass = new FirstClass(new OtherClass()); FirstClass.Method(); Console.ReadKey(); //tempClass temp = new OtherClass(); //temp.Method(); } } public class FirstClass { private tempClass _LastClass; public FirstClass(tempClass tempClass)//ctor { _LastClass = tempClass; } public void Method() { _LastClass.Method(); } } public abstract class tempClass{public abstract void Method();} public class LASTCLASS : tempClass { public override void Method() { Console.WriteLine("\nHello World!"); } } public class OtherClass : tempClass { public override void Method() { Console.WriteLine("\nOther World!"); } } } My_modified_code: namespace simple.main { class main { static void Main() { //FirstClass FirstClass = new FirstClass(new OtherClass()); //FirstClass.Method(); //Console.ReadKey(); tempClass temp = new OtherClass(); temp.Method(); } } //public class FirstClass //{ // private tempClass _LastClass; // public FirstClass(tempClass tempClass)//ctor // { // _LastClass = tempClass; // } // public void Method() // { // _LastClass.Method(); // } //} public abstract class tempClass{public abstract void Method();} public class LASTCLASS : tempClass { public override void Method() { Console.WriteLine("\nHello World!"); } } public class OtherClass : tempClass { public override void Method() { Console.WriteLine("\nOther World!"); } }

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  • Best practice to collect information from child objects

    - by Markus
    I'm regularly seeing the following pattern: public abstract class BaseItem { BaseItem[] children; // ... public void DoSomethingWithStuff() { StuffCollection collection = new StuffCollection(); foreach(child c : children) c.AddRequiredStuff(collection); // do something with the collection ... } public abstract void AddRequiredStuff(StuffCollection collection); } public class ConcreteItem : BaseItem { // ... public override void AddRequiredStuff(StuffCollection collection) { Stuff stuff; // ... collection.Add(stuff); } } Where I would use something like this, for better information hiding: public abstract class BaseItem { BaseItem[] children; // ... public void DoSomethingWithStuff() { StuffCollection collection = new StuffCollection(); foreach(child c : children) collection.AddRange(c.RequiredStuff()); // do something with the collection ... } public abstract StuffCollection RequiredStuff(); } public class ConcreteItem : BaseItem { // ... public override StuffCollection RequiredStuff() { StuffCollection stuffCollection; Stuff stuff; // ... stuffCollection.Add(stuff); return stuffCollection; } } What are pros and cons of each solution? For me, giving the implementation access to parent's information is some how disconcerting. On the other hand, initializing a new list, just to collect the items is a useless overhead ... What is the better design? How would it change, if DoSomethingWithStuff wouldn't be part of BaseItem but a third class? PS: there might be missing semicolons, or typos; sorry for that! The above code is not meant to be executed, but just for illustration.

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  • Haskell - mapping the odd placed values and the even placed values differently

    - by Abstract
    Hey guys, is there an easy way. To take a list of numbers, say 123456. Then multiply the odd placed by three and the even placed by 1. i.e. (1 * 3) + (2 * 1) + (3 * 3) + (4*1) + (5*3) + (6*1) i was thinking the map function somewhere along the lines. But i don't know how to map *3 to just the odd placed values. Oh and if you could give me the version not in prelude that would be great like the actual function or functions, as if its being imported from an external haskell file Thanks for the help

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  • Haskell - interpreting a number

    - by Abstract
    I have a number 9877342931235. Using Haskell, I need to show it as: 987-734293-123-5 i've tried interspersing the list but of course that puts '-' between every digit. How would I do it to yield the actual result?

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  • Oracle OpenWorld Call for Papers is Now Open through April 9th!

    - by Di Seghposs
    Get Your Papers Ready!! The OpenWorld 2012 Call for Papers is Now Open!! Interested in sharing your Oracle UPK story at the most important educational conference of 2012? Customers or partners who would like an opportunity to speak at OpenWorld should submit an abstract. If your session is selected, Oracle will waive the conference registration fee – saving you anywhere from $1,795 to $2,595. For details about the conference, visit the Oracle OpenWorld website.          Click here to submit your OpenWorld Session Abstract. Don't delay -- submit your abstract today - the Call for Papers closes on April 9, 2012 - Share your Oracle UPK Success Story at Oracle OpenWorld!

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  • Should concrete classes avoid calling other concrete classes, except for data objects?

    - by Kazark
    In Appendix A to The Art of Unit Testing, Roy Osherove, speaking about ways to write testable code from the start, says, An abstract class shouldn't call concrete classes, and concerete classes shouldn't call concrete classes either, unless they're data objects (objects holding data, with no behavior). (259) The first half of the sentence is simply Dependency Inversion from SOLID. The second half seems rather extreme to me. That means that every time I'm going to write a class that isn't a simple data structure, which is most classes, I should write an interface or abstract class first, right? Is it really worthwhile to go that far in defining abstract classes an interfaces? Can anyone explain why in more detail, or refute it in spite of its benefit for testability?

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  • Reminder - Only 5 Days Left! Oracle OpenWorld Call for Papers Closes April 9th

    - by Di Seghposs
    The OpenWorld 2012 Call for Papers is closing on April 9th!  Don't forget to submit your paper to share your Oracle UPK story at OpenWorld San Francisco! Customers or partners who would like an opportunity to speak at OpenWorld should submit an abstract. If your session is selected, Oracle will waive the conference registration fee – saving you anywhere from $1,795 to $2,595. For details about the conference, visit the Oracle OpenWorld website.          Click here to submit your OpenWorld Session Abstract. Don't delay -- submit your abstract today - the Call for Papers closes on April 9, 2012!

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  • Instantiating Interfaces in C#?

    - by RealityDysfunction
    I am reading/learning about interfaces in C# at the moment, and thus far I managed to understand how it differs from an abstract class. In the book I am reading the author explains that interfaces are the ultimate abstract class and that it simply sets the standard of certain methods the inheriting class will have, but then provides the following example... static void Main(string[] args) { ... Circle c = new Circle("Lisa"); IPointy itPt = null; try { itPt = (IPointy)c; Console.WriteLine.(itPt.Points); } catch (InvalidCastException e) { Console.WriteLine(e.Message); } ... } The line that absolutely throws me off is the "IPointy itfPt=null;" did he just declare an interface??? I thought interfaces are abstract and can only be inherited? What kind of sorcery is going on here? Thanks for any help, I

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  • Oracle OpenWorld Call for Papers is Now Open through April 9th!

    - by Pam Petropoulos
      The OpenWorld 2012 Call for Papers is Now Open!! The most important educational conference of 2012 is fast approaching and you have an opportunity to share your AutoVue success story. Customers or partners interested in presenting during Oracle OpenWorld 2012 should submit a presentation abstract. If your session is selected, Oracle will waive the conference registration fee – saving you anywhere from $1,795 to $2,595. For details about the conference, visit the Oracle OpenWorld website. Don't delay -- submit your presentation abstract today - the Call for Papers closes on Monday, April 9, 2012.   Click here to submit your OpenWorld Presentation Abstract Oracle OpenWorld 2012 takes place in San Francisco, CA from September 30 - October 4, 2012.

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  • Getting BeautifulSoup to find a specific <p>

    - by Ryan
    I'm trying to put together a basic HTML scraper for a variety of scientific journal websites, specifically trying to get the abstract or introductory paragraph. The current journal I'm working on is Nature, and the article I've been using as my sample can be seen at http://www.nature.com/nature/journal/v463/n7284/abs/nature08715.html. I can't get the abstract out of that page, however. I'm searching for everything between the <p class="lead">...</p> tags, but I can't seem to figure out how to isolate them. I thought it would be something simple like from BeautifulSoup import BeautifulSoup import re import urllib2 address="http://www.nature.com/nature/journal/v463/n7284/full/nature08715.html" html = urllib2.urlopen(address).read() soup = BeautifulSoup(html) abstract = soup.find('p', attrs={'class' : 'lead'}) print abstract Using Python 2.5, BeautifulSoup 3.0.8, running this returns 'None'. I have no option of using anything else that needs to be compiled/installed (like lxml). Is BeautifulSoup confused, or am I?

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  • rails question find no result

    - by Small Wolf
    Hey.Guys! Now .I have a question ,i want someone to help me to solve it ,the log of the problem like the under text >> Department.find(EmeReference.find(:all,:select =>:ref_config_id,:conditions=>"emergency_id = 1")) ActiveRecord::RecordNotFound: Couldn't find Department with ID=0 from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/base.rb:1591:in `find_one' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/base.rb:1574:in `find_from_ids_without_cache' from (__DELEGATION__):2:in `__send__' from (__DELEGATION__):2:in `find_from_ids_without_cache' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/query/abstract.rb:158:in `find_from_keys' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/query/primary_key.rb:31:in `miss' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/query/abstract.rb:66:in `hit_or_miss' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/accessor.rb:17:in `call' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/accessor.rb:17:in `fetch' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/accessor.rb:29:in `get' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/query/abstract.rb:65:in `hit_or_miss' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/query/abstract.rb:18:in `perform' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/query/primary_key.rb:17:in `perform' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/query/abstract.rb:7:in `perform' from /usr/lib/ruby/gems/1.8/gems/nkallen-cache-money-0.2.5/lib/cash/finders.rb:29:in `find_from_ids' from /usr/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/base.rb:616:in `find' from (irb):135 that's the question! Thank your and best regards!

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  • Java Generics name clash, method not correctly overriden

    - by Shervin
    Hi. I have seen different questions regarding this, but I still find this topic to be very confusing. All I want to do, is have an abstract class that implements an interface, and have a class extending this abstract class so that the hard class needs to implement getKommune() and setKommune(Kommune kommune), but not the other method, because that is in the abstract class. I have the following interface. public interface KommuneFilter { <E extends AbstractKommune<?>> void addKommuneFromCurrentUser(E e); Kommune getKommune(); void setKommune(Kommune kommune); } And this Abstract class public abstract class AbstractKommune<E extends AbstractKommune<?>> implements KommuneFilter { @PrePersist void addKommuneFromCurrentUser(E e) { } } And I want to use it like this public class Person extends AbstractKommune<Person> { private Kommune kommune; public void setKommune(Kommune kommune) {this.kommune=kommune;} public Kommune getKommune() {return kommune;} } However, I get Name clash: The method of has the same erasure of type but does not override it Why isn't it correctly overriden?

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  • Spring.net is not injecting chained base class properties!

    - by JohnIdol
    I am successfully injecting base class properties with spring.net with just a class that inherits from a base abstract class. Lets say Class MyClass : MyBase, and I am successfully setting a property like this: <object id="myInstantiableClass" type="myAssembly.MyClass myAssenbly" abstract="true"> <property name="MyBaseClassProperty" ref="anotherObjRef"></property> </object> Where MyBaseClassProperty is a property on the base class. Now I have another abstract class between the old base class and the instantiable class, and I am trying to set properties on both the abstract classes. So MyClass : MyNewBaseClass, and MyNewBaseClass : MyBaseClass. I have an additional property on the new base class (MyNewBaseClassProperty) and I am trying to inject it like this: <object id="myInstantiableClass" type="myAssembly.MyClass myAssenbly" abstract="true"> <property name="MyBaseClassProperty" ref="anotherObjRef"></property> <property name="MyNewBaseClassProperty" ref="someOtherObjRef"></property> </object> The property on the old base class is being injected but the one on the new one is not - and I am not getting an error or anything (so I am pretty sure my config is good), that property is just null! Any help appreciated! P.S. I am on asp.net (not MVC) but I don't think it's related.

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  • Spring: Using "Lookup method injection" for my ThreadFactory looks not scalable.

    - by Michael Bavin
    Hi, We're building a ThreadFactory so everytime a singleton controller needs a new thread, i get a new instance everytime. Looking at Lookup method injection looks good but what if we have multiple threads. like: public abstract class ThreadManager { public abstract Thread createThreadDoA(); public abstract Thread createThreadDoB(); } and config: <bean id="threadManager" class="bla.ThreadManager" singleton="true"> <lookup-method name="createThreadA" bean="threadA" /> <lookup-method name="createThreadB" bean="threadB"/> </bean> <bean id="threadA" class="bla.ThreadA"> <bean id="threadB" class="bla.ThreadB"> and usage: threadManager.createThreadA(); I don't want to create an abstract "create" method for every new threadclass. Is it possible to make this generich like: threadManager.createThread(ThreadA.class); Thank you

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  • Strange Scala error.

    - by Lukasz Lew
    I tried to create abstract turn based Game and abstract AI: abstract class AGame { type Player type Move // Player inside def actPlayer : Player def moves (player : Player) : Iterator[Move] def play (move : Move) def undo () def isFinished : Boolean def result (player : Player) : Double } abstract class Ai[Game <: AGame] { def genMove (player : Game#Player) : Game#Move } class DummyGame extends AGame { type Player = Unit type Move = Unit def moves (player : Player) = new Iterator[Move] { def hasNext = false def next = throw new Exception ("asd") } def actPlayer = () def play (move : Move) { } def undo () { } def isFinished = true def result (player : Player) = 0 } class DummyAi[Game <: AGame] (game : Game) extends Ai[Game] { override def genMove (player : Game#Player) : Game#Move = { game.moves (player).next } } I thought that I have to use this strange type accessors like Game#Player. I get very puzzling error. I would like to understand it: [error] /home/lew/Devel/CGSearch/src/main/scala/Main.scala:41: type mismatch; [error] found : Game#Player [error] required: DummyAi.this.game.Player [error] game.moves (player).next [error] ^

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  • PHPUnit: Testing if a protected method was called

    - by Luiz Damim
    I´m trying to test if a protected method is called in a public interface. <?php abstract class SomeClassAbstract { abstract public foo(); public function doStuff() { $this->_protectedMethod(); } protected function _protectedMethod(); { // implementation is irrelevant } } <?php class MyTest extends PHPUnit_Framework_TestCase { public function testCalled() { $mock = $this->getMockForAbstractClass('SomeClass'); $mock->expects($this->once()) ->method('_protectedMethod'); $mock->doStuff(); } } I know it is called correctly, but PHPUnit says its never called. The same happens when I test the other way, when a method is never called: <?php abstract class AnotherClassAbstract { abstract public foo(); public function doAnotherStuff() { $this->_loadCache(); } protected function _loadCache(); { // implementation is irrelevant } } <?php class MyTest extends PHPUnit_Framework_TestCase { public function testCalled() { $mock = $this->getMockForAbstractClass('AnotherClass'); $mock->expects($this->once()) ->method('_loadCache'); $mock->doAnotherStuff(); } } The method is called but PHPUnit says that it is not. What I´m doing wrong? Edit I wasn´t declaring my methods with double colons, it was just for denoting that it was a public method (interface). Updated to full class/methods declarations. Edit 2 I should have said that I´m testing some method implementations in an abstract class (edited the code to reflect this). Since I can not instantiate the class, how can I test this? I´m thinking in creating an SomeClassSimple extending SomeClassAbstract and testing this one instead. Is it the right approach?

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  • NullPointerException with static variables

    - by tomekK
    I just hit very strange (to me) behaviour of java. I have following classes: public abstract class Unit { public static final Unit KM = KMUnit.INSTANCE; public static final Unit METERS = MeterUnit.INSTANCE; protected Unit() { } public abstract double getValueInUnit(double value, Unit unit); protected abstract double getValueInMeters(double value); } And: public class KMUnit extends Unit { public static final Unit INSTANCE = new KMUnit(); private KMUnit() { } //here are abstract methods overriden } public class MeterUnit extends Unit { public static final Unit INSTANCE = new MeterUnit(); private MeterUnit() { } ///abstract methods overriden } And my test case: public class TestMetricUnits extends TestCase { @Test public void testConversion() { System.out.println("Unit.METERS: " + Unit.METERS); System.out.println("Unit.KM: " + Unit.KM); double meters = Unit.KM.getValueInUnit(102.11, Unit.METERS); assertEquals(0.10211, meters, 0.00001); } } 1) MKUnit and MeterUnit are both singletons initialized statically, so during class loading. Constructors are private, so they can't be initialized anywhere else. 2) Unit class contains static final references to MKUnit.INSTANCE and MeterUnit.INSTANCE I would expect that: KMUnit class is loaded and instance is created. MeterUnit class is loaded and instance is created. Unit class is loaded and both KM and METERS variable are initialized, they are final so they cant be changed. But when I run my test case in console with maven my result is: T E S T S Running de.audi.echargingstations.tests.TestMetricUnits Unit.METERS: m Unit.KM: null Tests run: 3, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.089 sec <<< FAILURE! - in de.audi.echargingstations.tests.TestMetricUnits testConversion(de.audi.echargingstations.tests.TestMetricUnits) Time elapsed: 0.011 sec <<< ERROR! java.lang.NullPointerException: null at de.audi.echargingstations.tests.TestMetricUnits.testConversion(TestMetricUnits.java:29) Results : Tests in error: TestMetricUnits.testConversion:29 NullPointer And the funny part is that, when I run this test from eclipse via JUnit runner everything is fine, I have no NullPointerException and in console I have: Unit.METERS: m Unit.KM: km So the question is: what can be the reason that KM variable in Unit is null (and in the same time METERS is not null)

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  • Is it good to subclass a class only to separate some functional parts?

    - by prostynick
    Suppose we have abstract class A (all examples in C#) public abstract class A { private Foo foo; public A() { } public void DoSomethingUsingFoo() { //stuff } public void DoSomethingElseUsingFoo() { //stuff } //a lot of other stuff... } But we are able to split it into two classes A and B: public abstract class A { public A() { } //a lot of stuff... } public abstract class B : A { private Foo foo; public B() : base() { } public void DoSomethingUsingFoo() { //stuff } public void DoSomethingElseUsingFoo() { //stuff } //nothing else or just some overrides of A stuff } That's good, but we are 99.99% sure, that no one will ever subclass A, because functionality in B is very important. Is it still good to have two separate classes only to split some code into two parts and to separate functional elements?

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  • Mixing table per subclass and per hierarchy in hibernate

    - by Xelluloid
    In my database there are two three tables. The first one, table ABSTRACT, holds three columns id, type, someText This table contains all abstract information for the abstract class abstract. Now the two tables CONCRETEONE and CONCRETETWO contain all information for the concrete classes concreteOne and concreteTwo. Now I know I could use the table per subclass strategy from hibernate to create a mapping with inheritance. But as I have a column that marks the type of the concrete implementation could it be possible to create some mixed behaviour like a table per subclass strategy with an discriminator?

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  • Set property with reflection after Fluent Nhibernates automapping has occured?

    - by Marcus
    I have an abstract baseclass with a collection of details IList that is automapped with fnh. After it has been populated with the correct values i would like to set some properties with reflection on the my class that inherits the abstract baseclass. I have tried to accomplish this in the constructor of my abstract baseclass but obviously my Details collection is empty when the occurs so my question is, what is the recommended way of doing this?

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  • C# Virtual method call in constructor - how to refactor?

    - by Cristi Diaconescu
    I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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